1. Field of the Invention
The present invention relates to material detection and more particularly to trace material extraction, analysis and detection.
2. Background of the Invention
Increasing sophistication of explosive devices being used domestically and in the foreign arenas make detection of such explosive devices difficult using classical detection devices. Characteristics of the material in which an explosive device is hidden prior to detonation, or buried in the case of an improvised explosive device in a combat zone, can also act to defeat classical detection devices. For example, vapor typically given off by an explosive may adhere to the material or soil in which the explosive is hidden such that vapor pressure alone can not be relied on to provide a sample that can be tested for the presence of an explosive. In addition, non-nitrogen based explosives may even be undetectable using conventional detection devices. The importance of detecting an explosive prior to detonation can not be understated due to the resultant effects of detonation when the explosive is used as a weapon.
Further, determination after explosive detonation of the presence of an explosive and/or explosive residue suitable for testing is extremely difficult. Samples available for analysis after an explosion are minimal at best and contamination during extraction and testing of the samples is extremely critical as levels of sample mass and volume decrease. Direct identification and trace of the explosive utilized in the explosive device after the fact is thus still more difficult.
During extraction and detection, significant mechanisms of contamination (and depletion of sample mass) between a solid surface and a fluid/gas include adherence, as mentioned above, and absorption. A sample may be depleted when particles are retained by frictional phenomena such as adherence to surfaces/s from mechanical “roughness” of surface topology. A sample may also be depleted by adherence to surface/s resulting from “physical adsorption” forces, such as van der Waals forces, the same as those which produce liquefaction. Sample depletion may also occur due to adherence to surface/s resulting from chemisorption; the adsorbed molecules react chemically with the surface, not beyond formation of a monolayer on the surface. Absorption through surfaces from diffusion also depletes samples, wherein the adsorbed molecules are moved to below solid surfaces to some state of kinetic equilibrium. These and other mechanisms result in the ratio of mass of the target material in the sample that absorbed (within a surrounding environment or on collection/extraction equipment) to mass of the target material in the sample that is desorbed (i.e., available for analysis) not always being 1:1.
Mass spectrometry provides the ability to characterize a physical sample and determine its composition via a measurement of mass-to-charge ratio of ions. The most popular mass spectrometer is the transmission quadrupole mass spectrometer which consists of two sets of parallel surfaces arranged so that the cross section forms two hyperbolae orthogonal to each other. These four conducting surfaces are the poles and can be manufactured as rods with the hyperbolic surface, as round rods, or as a single-quartz mandrel having the orthogonally positioned two-hyperbolae cross section with conducting material vapor deposited on the appropriate surfaces.
Hyperbolic electrodes are typically made from quartz which is ground into the desired geometry. Quartz is utilized because it has one of the lowest thermal expansions, which is necessary to maintain the hyperbolic shape. The hyperbolic quartz electrode is covered with multiple layers of titanium composite and gold. Unfortunately, rods with hyperbolic profiles are difficult to produce and fragile. Round (cylindrical) rods can be machined and manufactured from more rugged materials but the calculations necessary to determine the trajectory of the ions requires enormous computing power (which may require considerable expense and/or time) or a significant trade off in accuracy and resolution.
These factors and others contribute to the difficulty in being able to rapidly, efficiently and effectively detect dangerous substance/s. Rapid detection of the presence of a dangerous substance, such as detection of an explosive prior to the devastating consequences of the substance becoming present (i.e., detonation of an explosive device), is critically important and necessary to provide the safety and security the public demands.